Chemotherapy regimens which utilize conventional drugs for the treatment of non-small cell lung cancer can achieve response rates in the range of 20-40%. Despite these promising response rates, phase III studies which compare best supportive care to chemotherapy in non-small cell lung cancer have shown a maximum prolongation of survival of only 16 weeks. In this setting, the need to develop new, more effective first-line chemotherapy regimens for non-small cell lung cancer is clear. Studies performed in patients with small cell lung cancer and leukemia have demonstrated that patients' likelihood of responding to conventional chemotherapy regimens is not impaired by initial treatment with an investigational agent. Accordingly, this trial has been developed as first line therapy for patients with advanced non-small cell lung cancer. Patients who enroll in this trial and subsequently receive second line chemotherapy will be followed to determine their rate of response to such treatment. The objectives of this trial are to: 1)To determine if 9-aminocamptothecin colloidal dispersion administered as a 120 hour weekly infusion is an effective agent of treatment of advanced non-small cell lung cancer. 2)To observe the toxicity associated with this regimen among patients with advanced nonsmall cell lung cancer. 3) To measure the levels of topoisomerase I in tumor biopsy specimens obtained from patients with non small cell lung cancer entered on this trial. 4) To determine the 9-AC pharmacokinetics parameters and to correlate serum levels with toxicity and response to treatment. 5) To determine the mutagenic potential of 9-AC administered as a 120hr weekly infusion. Patients will receive a 5 day continuous intravenous chemotherapy treatment. After a 2 day rest, 9-AC will be repeated for a total of 3 weeks followed by a one week rest period. The 9-AC treatment will be repeated for as long as the tumor continues to shrink or remains stable, unless limiting side effects occur. Blood samples will be drawn prior to and following each treatment. The pharmacokinetic studies will be conducted on the GCRC.